using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<int> a = new List<int> {1,2,3,4,5,6};

                List<int> b = new List<int> {1,2,3,6};

        var c = a.Where(x=> !b.Contains(x)).ToList();

​

        for(int i=0; i<c.Count; i++){

                    Console.WriteLine(c[i]);

​

        }

    }

}